Apparatus and method for making a slurry



Aug. 5, 1969 H. c. c. KARTMAN APPARATUS AND METHOD FOR MAKING A SLURRYFiled May 5, 1966 FIG. 2

INVENTOR. HELGE CARL CHRlSTAN KARTMAN m ATTORN EYS United States Patent3,459,380 APPARATUS AND METHOD FOR MAKING A SLURRY Helge Carl ChristianKartman, Copenhagen-Valby, Denmark, assignor to F. L. Smidth & Co., NewYork, a corporation of Delaware Filed May 3, 1966, Ser. No. 547,331Claims priority, application Great Britain, May 4, 1965, 18,748/65 Int.Cl. B28c 1/02 US. Cl. 241-43 8 Claims ABSTRACT OF THE DISCLOSURE Acombined wash and grinding mill which is divided into at least twocompartments by a hollow sieve ring. One compartment is used forinitially preparing a slurry of required fineness for separation out ofthe hollow sieve ring and a second compartment is used forsimultaneously washing and autogenously grinding the remaining slurry.

This invention relates to an apparatus and method for making a slurry.More particularly it relates to a mill divided into compartments by atleast one sieve member to form at least two compartments, onecompartment for initially preparing a slurry of required fineness forseparation out of the hollow sieve ring and a second compartment forwashing and autogeneous grinding of the unseparated slurry; it furtherrelates to a method of preparing a slurry by first preparing a slurryfrom solid materials and water, separating slurry of the desiredfineness therefrom, and simultaneously washing and autogeneouslygrinding the remaining slurry.

The invention has particular applicability to the preparation of mineralslurries in the manufacture of cement, lime and the like, but can beused in any manufacturing processes in which a mixture of materials isconverted to a homogeneous aqueous slurry.

Heretofore, in the reduction of solid materials mixed with a liquid in awet mill to form a wet slurry such as in the preparation of mineralslurries in the manufacture of cement, lime and the like, difficulty hasbeen experienced in removing any coarse material present from the slurryleaving the mill. To compensate for this and to obtain a homogeneousslurry, the practice has been to screen the product from the mill bysieves built into the mill outlet or in a separate process performedentirely outside the mill. The use of sieves at the outlet from themill, although most frequently chosen, suffers from the disadvantagethat the coarse unground material tends to accumulate in largequantities inside the mill and this interferes with the proper functionof the mill itself. These interferences mainly consist of periodicshut-down of the mill in order to clear the material and thissubstantially reduces the production capacity of the mill. The use ofoutside separation is costly in that it involves substantial additionaloutlays for machinery, which adds appreciably to production costs.

It is an object of the invention to solve these problems by sieving fineslurry from the mill as it is being formed and reaches the desiredfineness in at least one first compartment and then transferring theremaining coarser material to a second compartment where additionalwater is added and the coarser material is subjected to a simultaneouswashing and autogeneous grinding with the fine slurry produced in thiscompartment being sieved and the nibs of coarse material formed duringgrinding being removed through a separate outlet. With the presentinvention the slurry can be formed on a continuous basis without needfor frequent shut-down as formerly was necessary.

Patented Aug. 5, 1969 Broadly stated the apparatus of the invention isin a combined wash and grinding mill for making a slurry from solidmaterial and water and separating the fine slurry from the mill as it isformed. The mill is comprised of a rotatable tubular mill housing withan inlet in the housing for feeding solid material and water therein. Atleast one internal sieving dam member is secured to the inside wall ofthe housing and forms at least two axially separated compartments onopposite sides of the dam member. The dam member has axially spacedsieve portions facing each compartment for receiving fine slurry fromboth adjoining compartments; and the spaced sieve portions define ahollow collection chamber therebetween in which the separated slurry iscollected as it passes through the sieve portions. Slurry outlet meansare connected to the hollow collection chamber for feeding the collectedslurry therefrom. A conduit extends through the dam member fortransferring coarse materials into the next compartment. Means areprovided for feeding water into the compartment adjacent the outlet endof the housing for simultaneously washing and autogeneously grinding ofthe slurry and means are provided for transferring nibs of coarsematerial from the mill at its outlet end.

The housing is preferably cylindrically mounted at both ends with hollowtrunnions which serve as the inlet and outlet for the mill and the dammembers are ring shaped with a conduit extending through the hub of thering and have annular sieve portions surrounding the conduit. Aperipheral outlet is formed through the casing and into the collectionchamber. It is further preferred to form the darn ring from two dishedmembers which have hollow joined hubs that form the conduit.

The method of the invention lies in making an aqueous slurry andcomprises feeding solid material and water to at least one mixing zoneto form a slurry and sieving fine slurry from this zone while conveyingcoarser material to a grinding zone; water is added to the coarsermaterial in the grinding zone and fine slurry is separately sieved whilenibs of coarse material remaining after grinding are removed from thegrinding zone.

It is also preferred to feed the slurry through two mixing zones whilecontinuously sieving material from these mixing zones as it is formed.

In a mill according to the invention, the coarse material does notinterfere with the outflow of slurry from the first compartments of themill and any accumulation of coarse particles in the last compartment isno drawback since the presence of the coarse materials in the lastcompartment subjects particles to more effective autogeneous grinding.The main part of the coarse resistant material conveyed to the lastcompartment of the mill is crushed during the autogeneous grinding but asmall portion, commonly called nibs, may remain uncrushed. These nibsare discharged through the mill outlet thereby keeping a high slurrylevel in the mill while avoiding slurry spill. Water is added to thegrinding compartment to facilitate passage of slurry from thecompartment.

A preferred embodiment of the invention is described hereinbelow withreference to the drawing wherein:

FIG. 1 is a sectional view along the axis of the mill; and

FIG. 2 is a section taken along the lines 22 of FIG. 1.

A grinding mill 10 is shown and is constructed of a general cylindricalhousing 11 which has hollow inlet and outlet trunnions 12 and 13extending axially from an inlet end 14 and outlet end 15 of the mill.The inlet and outlet trunnions are carried in bearings 16 and 17 so thatthe entire housing is freely rotatable by any suitable drive meanscommon to the art and not shown. Connected to the inlet hollow trunnion12 is an elbow connection 18 which has a funnel shaped inlet end intowhich solid or semi-solid material such as cement raw material and limecan be introduced with water through a water pipe 19 for feed into thehousing 11.

The housing 11 has an inner lining 20 and it is divided into threecompartments 21, 22 and 23 by two axially spaced sieving dam rings 24and 25 which are of identical construction, and thus a description ofonly one is necessary.

The sieving dam ring is constructed of two dished annular sieve plates26 and 27 which converge inwardly toward each other and are joined attheir hollow hub portion to form a center conduit 28 which extendsaxially through the center of the dam ring. The outer rims 29 and 30 ofthe respective sieve plates are fixed to the inner lining of the housingand therefore rotate with the housing. The dished annular sieved plateshave a series of concentrically spaced arcuate slots 31 which areconcentrically spaced around the plate and increase in width from thecenter to the outer rim 29. Each radial progression of slots isseparated by a radially extending solid bar 32. The space between thesieve plates defines a collection chamber 33 into which fine slurry, thesize of which is dependent on the slot openings, is fed into thecollecting chamber from either side of the dam ring. Underlying thecollecting chamber at the bottom of the housing 11 is a slurry outletopening 34. The entire periphery surrounding the dam ring is enclosed ina stationary casing 35 which provides a reservoir for the slurry beingfed from the peripheral outlet 34 of the collecting chamber.

Mounted on the inner linings of the housing which is adjacent to theinlet end of the dam rings 24 and 25 are lifter plates 36 and 37 whichare circumferentially spaced around the lining of the casing. Thelifting plates are inclined toward the outlet end of the housing.Secondary lifter plates 38 and 39 are mounted on the face of the annularsieve plates and are circumferentially spaced thereabout. These liftersadvance the slurry toward the outlet end of the mill and improve thesieve of fine slurry from the chambers and passage of the coarsermaterial to the respective compartments through the center conduit 28.

Lifter plates 40 similar to the lifter plates 36 and 37 are providedadjacent the outlet trunnion mill and secondary lifters 41 are providedon the end wall of the mill adjacent to the outlet trunnion 13 and theyfunction in a similar way to transfer the particles in the last chamberto the outlet trunnion. A water pipe 42 extends into the lastcompartment 23 through the outlet trunnion and has a spreader head 43for spraying water into the last compartment to form slurry in thiscompartment and facilitate transfer of the slurry through the sieve damring 25.

Although two sieve dam rings are shown, it is possible to form agrinding mill with a single dam ring which would separate the housinginto two compartments.

In operation, the solid material and water are mixed in the firstchamber 21 to form a slurry, some of which is of the fineness desiredand other is too coarse. The lifters 36 and secondary lifters 38transfer the material in the first compartment against the sieve plateand slurry of the required fineness passes into the sieve plate and intothe chamber where it is peripherally discharged through outlet 34 andinto casing 35. Coarser material passes through the conduit 28 and intothe second mixing chamber 22. Further mixing occurs in the secondarychamber and the material is again contacted against the secondary sievedarn ring 25 again separating slurry of the desired fineness. In thissecond chamber 22, the slurry is also in contact with the outlet side ofthe first sieve dam ring and fine slurry is separated through the firstsieve dam ring at the same time.

Substantially, all the fine slurry is removed in the first or secondchambers and mainly coarse material passes through conduit 28 of thesecond dam ring and is transferred to the third compartment 23 which isa grinding compartment for autogeneous grinding of the coarse material.Water is sprayed into this last compartment to form additional slurrywith the fine particles that are broken up during grinding and thisadditional fine slurry will pass into the sieve dam ring by contactingthe sieve plate on the outlet side of the second dam ring. Coarsematerial will finally be conveyed by use of the lifters 41 through theoutlet trunnion of the grinding mill.

I claim:

1. A combined wash and grinding mill for making a slurry from solidmaterial and water and separating fine slurry from the mill as it isformed comprising a rotatable tubular mill housing, an inlet into saidhousing for feeding solid material and water therein, at least oneinternal sieving dam member secured to the inside wall of the housingforming at least two axially separated compartments on opposite sides ofthe member, axially spaced sieve portions of said member facing eachcompartment for receiving fine slurry from both adjoining compartmentsand defining a hollow collection chamber therebetween in which theseparated slurry 1s collected as it passes through the sieve portions,outlet means connected to said hollow collection chamber for feeding theslurry therefrom, a conduit extending through said darn member fortransferring coarse material into the next compartment, means forfeeding water into the compartment adjacent the outlet end of thehousing for simultaneous washing and autogeneous grinding of the slurry,and means for transferring nibs of coarse material from the mill at itsoutlet end.

2. A grinding mill according to claim 1 wherein two axially spaced dammembers are mounted in the housing thereby forming three compartments.

3. A grinding mill according to claim 1 wherein said tubular housing isgenerally cylindrical, said dam members are ring shaped with conduitextending through the hub of the ring and annular sieve portionssurrounding the conduit, and a peripheral outlet is formed through thecasing into said collection chamber.

4. A grinding mill according to claim 3 wherein the darn ring is formedfrom spaced dished members which have hollow hubs that are joined toform said conduit.

5. A grinding mill according to claim 3 wherein said peripheral outletfrom said collecting chamber is surrounded by a stationary outletcasing.

6. A grinding mill according to claim 3 wherein the mill inlet extendsinto the first compartment through a first hollow trunnion and said milloutlet extends from the last compartment through a second hollowtrunnion.

7. A grinding mill according to claim 3 wherein lifter means areprovided adjacent the inlet side of the sieve darn ring for feedingslurry against the dam ring and through the conduit.

8. A grinding mill according to claim 5 wherein lifter means areprovided around the outlet on the end of the mill housing for feedingthe solid material to the outlet.

References Cited UNITED STATES PATENTS 1,748,920 2/1930 Newhouse 241-72X 1,902,413 3/1933 Miller 241-70 X 2,031,710 2/ 1936 Ihlefeldt 241-452,160,169 5/1939 Pontoppidan 241-72 FOREIGN PATENTS 478,057 6/ 1929Germany. 682,447 10/ 1939 Germany.

W. GRAYDON ABERCROMBIE, Primary Examiner US. Cl. X.R.

